1. Field of the Invention
The present invention relates in general to apparatus for holding a specimen, such as a laboratory animal, in a fixed position during an imaging procedure such as X-ray, CAT, and CT scans and MRI and PET imaging. The invention relates in particular to such apparatus which provide for the accurate repeatable positioning of a specimen time and again within the same imaging machine or within a number of different imaging machines.
2. Description of Prior Developments
Medical researchers and other investigators often use laboratory animals such as rats, mice and other rodents in the course of various studies and investigations. Such studies sometimes require the use of imaging machines to produce a series of images of one or more anatomical features of the specimen over a period of time. Images of the brain, heart and other organs as well as musculoskeletal features are commonly repeatedly imaged over a period of time.
In order to take accurate, repeatable images of the same area of the specimen, the specimen must be held tightly in the same position relative to the imaging apparatus. In the past, a pair of retention bars or retention screws was snugly inserted within a rodent's ears for holding the rodent in a relatively fixed position during imaging.
A problem can arise with the use of conventional ear bars when a specimen must be imaged within a small, tight enclosure, such as within a small diameter bore of a small imaging coil in an MRI machine. Small bore imaging coils are desirable for imaging small specimens such as laboratory rodents because, in general, the smaller the bore of the imaging coil, the better is the clarity of an image.
As conventional ear bars or ear screws extend laterally or radially outwardly when placed within the bore of an imaging coil, they can limit the use of conventional specimen holders to larger bore imaging coils, and larger imaging machines with larger imaging areas. Moreover, relatively large conventional ear bars can interfere with the placement of small gradient coils around the head area of a specimen.